Cut back on heavy meals and increase your intake of water. Warm water helps to get things moving. Continue drinking until you feel movement in your lower intestine. Staying active helps as well.
It is commonly heard to consume more fibre but only do this if you plan on drinking just as much water, otherwise it can make things worse.
And if you're really desperate, try a gentle laxative. Something with marshmallow root, cascara bark or slippery elm should do the trick. Once you're feeling better, pay closer attention to what you drink and eat throughout the week. Try to keep a balanced diet.
Treat the cause and not the symptoms! More info is required.